It is well known that a mixture of fluids having different densities may be separated from one another through use of a centrifugal separator. One specific use of such a separator is in the separation of oil from gas vented from a crank case forming part of an internal combustion engine.
With regard to this specific use of separators, there can be a tendency for the high pressure gasses found in the combustion chambers of an internal combustion engine to leak past the associated piston rings and into the crank casing of the engine. This continuous leaking of gas into the crank case can lead to an undesirable increase of pressure within the crank case and, as a consequence, to a need to vent gas from the casing. Such gas vented from the crank casing typically carries a quantity of engine oil (as droplets or a fine mist), which is picked up from the reservoir of oil held in the crank casing.
In order to allow vented gas to be introduced into the inlet system without also introducing unwanted oil (particularly into a turbocharging system wherein the efficiency of the compressor can be adversely affected by the presence of oil), it is necessary to clean the vented gas (i.e. to remove the oil carried by the gas) prior to the gas being introduced into the inlet system. This cleaning process may be undertaken by a centrifugal separator, which is mounted on or adjacent the crank case and which directs cleaned gas to the inlet system and directs separated oil back to the crank case. An example of such a separator is disclosed e.g. in U.S. Pat. No. 8,657,908.
However, when the centrifugal separator is used for cleaning crankcase gases from smaller combustion engines, such as smaller diesel engines used especially in lighter trucks and the like, there is a need for a separator that does not have a relatively large size requiring a large space. One way of reducing the size of the centrifugal separator is to reduce the diameter of the stack of separation disks. However, in order to maintain the separation efficiency, the height or the length of the stack then has to be increased.
Furthermore, an issue may also be to keep once separated particles from re-entering into the cleaned gas after the separation in e.g. a disc stack of the centrifugal separator.
There is thus a need in the art for centrifugal separators having a reduced or compact size while maintaining or improving the separation efficiency.